12 GeV Collaboration

12 GeV Upgrade Technical Scope

Schematic layout of the required facility modifications to realize the 12 GeV Upgrade.

The 12 GeV Upgrade is highly cost effective due to existing features
of the Continuous Electron Beam Accelerator Facility (CEBAF). The superconducting
radiofrequency linear accelerators contain superconducting niobium cavities operating,
on average, at 50 percent above their design specifications in accelerating gradient
and Q. The success of this technology opens up the possibility of a relatively simple,
inexpensive upgrade of CEBAF's top energy. This goal is also made possible due to
the CEBAF tunnel "footprint," which was designed so that the magnetic arcs could
accommodate an electron beam of up to 24 GeV.

The latent voltage of the installed superconducting cavities has brought CEBAF's accelerating performance to nearly 6 GeV and superconducting radiofrequency (SRF) development successes have led to two cryomodules that are a factor of two more powerful than the original design. A cryomodule development program has yielded a final design that exceeds the original design specification by a factor of five. The cryomodules to be used for the 12 GeV Upgrade use higher performing seven cell cavities while maintaining the overall length of the original cryomodule design. Using space already available in the accelerator tunnels, 10 final design higher performance cryomodules will be installed at a modest cost.

The new experimental Hall D will use the electron beam to produce a coherent
bremsstrahlung beam and house a solenoid detector to carry out a program in
gluonic spectroscopy to experimentally test current understanding of quark
confinement. All three existing halls will be upgraded to receive the new Five-pass,
11 GeV beam. The additional experimental equipment proposed for Halls A, B and C
take full advantage of currently installed apparatus.